Strands powdered by electrostatic method

ABSTRACT

The invention relates to a method and facility for manufacturing a tape of reinforcement filaments impregnated by a polymer matrix, as well as a tape produced thereby, said tape having a constant width across the entire length thereof, wherein the filaments extend in a direction parallel to the length of the tape, from a strand of filaments coming from a feeding reel. The method including steps and units that make it possible to manage the unwinding tension of the strand, to guide the strand on the axis of the machine, to manage the width of the strand, to deposit the polymer on the strand by electrostatic powdering, with a polymer weight ratio of around 20% to around 75% to melt the polymer, to calibrate the width and thickness of the tape and to collect the tape on the storage reel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.15/521,473, having a filing date of Apr. 24, 2017, which was a 371application of International application PCT/EP2015/074734 filed on Oct.26, 2015, which claimed the benefit of European patent application FR1460259, filed Oct. 24, 2014, all of said applications incorporatedherein by reference.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to the technical field of composites witha continuous reinforcement with a thermoplastic or thermosetting organicmatrix. It more particularly relates to semi-finished products used inthe manufacturing of composite materials by automated fiber placement(AFP) or by filamentary winding, pultrusion, braiding, 3D printing.These composites are intended for “indirect” methods, which means thatthe whole organic matrix of the final composite is already found on thesemi-finished product. Once the tape is deposited and carried out on thesupport, a perform is obtained which contains a certain percentage ofporosity according to the deposition parameters. Finally, depending onthe porosity level aimed in the final part and on the quality of thepreform, the step for consolidating the part is carried out in anautoclave or in an oven.

In the aeronautical, oil or automotive fields, it becomes imperative toautomate the manufacturing methods in order to gain in productivity, inaccuracy and therefore in quality in order to remain competitive inthese highly competitive sectors. Moreover, these sectors require highquality products with generally high mechanical properties. The use ofcarbon fiber and notably of unidirectional fibers gives the possibilityof meeting the requirements. However, the primordial parameter for theseapplications, once the requirements have been met, is the quality.Indeed, in aeronautics, all the structural parts are controlled at thedifferent manufacturing steps, the cost of non-qualities may then bevery significant. Moreover, the price of high performance materialsused, like carbon and the polymers with a high Tg, requires having avery low waste level in order to be competitive. Finally, for reducingthe machine idle times, the conditioning of the semi-finished productsshould be optimized, this notably requires the use of coils of greatlengths not containing any defects to be discarded during thedeposition. It is in order to meet these requirements that thesemi-finished products according to the invention have been developed.

This type of product is generally obtained in several steps which may becarried out separately or on line. The first step consists of obtaininga unidirectional carbon web formed with several strands of carbon. Oncethe filaments are aligned and the surface mass of carbon is adjusted,the web is immersed into a polymeric dispersion in a liquid phase, thisis the impregnation phase. Once the filaments are loaded with polymer,the web is heated in order to melt this polymer and to discharge theliquid phase. Finally, once the web is consolidated, it is cut out as atape with a controlled width, and then wound on coils. The majordrawbacks of this method is that the cutting out causes filaments to jutout from the edges of the tape and that, if the cutting out is notperfectly parallel to the filaments, the latter are not strictlyoriented in the longitudinal direction of the tape.

EP 1 007 309 describes the production of continuous tapes byimpregnation of thread strands in an inorganic material, of the carbonor glass type, in a bath of polymer with application of shearing. Thismethod aims at producing tape for the indirect method, with a polymerlevel ranging from 25 to 75% by weight. Example 1 describes the passageof a strand of glass threads in an impregnation bath, and then into adie of rectangular section with dimensions 0.64 cm×0.023 cm, forproducing a tape having these dimensions. Therefore this is animpregnation method via a molten route for which the production rate islimited (a rate attaining 1,676 cm/min is mentioned), wherein theimpregnation directly depends on the viscosity of the polymer and whichdoes not allow working with every types of polymers. Further, thismethod does not give the possibility of having coils with a great length(greater than 100 m) without making a «splice», which generatesdiscontinuities in the reinforcement and therefore potentially areduction of the mechanical properties. Other drawbacks are the energycost for removing the water or the solvent and the ecological impact inthe case of using a solvent.

SUMMARY OF THE INVENTION

An object of the invention is to produce and propose a reinforcementtape with a great length in a single piece, without any cutting out andwithout any splices, which may attain the length of the strand (tow) ofthe supply coil, for example which may attain and exceed 1,000 meters,while having a very regular width which may be characterized by a verysmall standard deviation and/or good management of the distribution ofthe polymer.

Another object of the invention is to produce and propose such a tapewith a controlled polymer level.

Another object of the invention is to produce and propose such a tapefor which the constitutive filaments are strictly parallel to thelongitudinal direction of the tape.

An object of the invention is therefore to propose a method giving thepossibility of continuously manufacturing such a tape.

Another object of the invention is to produce and propose such a tapewhich is flexible, notably for which the flexibility may easily beadjusted, and preferably which is non-brittle.

A further other object of the invention is to produce and propose such atape at a competitive price.

These objects are attained with a method for producing continuously atape from a strand of filaments. The object of the present invention isa method for manufacturing a tape of reinforcement filaments,impregnated with a thermoplastic or thermosetting polymer matrix, a tapewhich has a constant width over the whole of its length, wherein thefilaments extend along a direction parallel to the length of the tape.This method may be applied to the treatment of a strand from a supplycoil or simultaneously and in parallel of several (2 or more) strandsstemming from as many supply coils. The supply coils may notably be of atype currently used, most commonly a crossed coil (the strand is woundwith transverse and crossed winding) or optionally a coil with simpletransverse winding.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention will now be described in more detail by means ofembodiments taken as a non-limiting example and with reference to thedrawing wherein:

FIG. 1 is a schematic illustration of a facility according to theinvention.

FIGS. 2, 3 and 4 are schematic illustrations of different calibrationdevices according to the invention.

FIG. 5 is a schematic illustration of a tape produced by the standardmethod with impregnation in a bath.

FIG. 6 is a schematic illustration of a tape produced by a firstembodiment of the invention.

FIG. 7 is a schematic illustration of a tape produced by a secondembodiment of the invention.

FIGS. 8 and 9 are graphs representing the width measurements carried outevery 1 m of tape according to the metering in m produced.

FIG. 10 is a schematic illustration of a cross-section of a tapeincluding bundles of filaments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

This method is notably characterized in that it comprises, for eachstrand (one or several strands may be treated simultaneously), thefollowing manufacturing steps, from a supply coil with a strand up to acoil for storing the tape:

-   -   a) handling the tension between the supply coil and the storage        coil,    -   b) guiding the strand so as to orient a strand moving in        translation on a line coinciding with a longitudinal axis, a so        called machine axis, extending as far as the proximity of the        storage coil,    -   c) optionally a transverse spreading of the strand to a        predetermined width greater than the width of the tape,    -   d) handling the width of the strand,    -   e) optionally traction of the strand, preferably by pinching or        padding,    -   f) grounding the strand,    -   g) deposition of the polymer as a powder on the strand, by        electrostatic powder coating, preferably with a mass polymer        content of about 20% to about 75%, obtaining an impregnated        tape,    -   h) melting or softening the polymer,    -   i) width and thickness calibration of the tape,    -   j) optionally measurement of the width and/or of the thickness        of the tape,    -   k) winding the tape on the storage coil.

According to the invention, a strand is defined as consisting of anassembly of filaments (or fibers) and includes from about 1,000 to about80,000 filaments, preferably between 3,000 and about 24,000 filaments.The strands used within the scope of the invention preferably are in amaterial selected from among carbon, ceramics, glasses, silicas,basalts, and aramides, or further any other material used in the fieldof composite materials, for example metal filaments or fibers, thefilaments may be of natural or synthetic origin. Carbon is particularlypreferred. The ceramics which may be used are notably silicon carbideand refractory oxides, for example, alumina and zirconia. The initialstrand may appear as an already flattened shape or more or less round.Generally, the strands are shown in crossed wound flat strand coils. Ina preferred embodiment, carbon strands are used comprising from about1,000 to about 80,000 filaments, preferably from about 3,000 and about24,000 filaments.

The flat composite formed with the strand and with the thermoplastic orthermosetting polymer is called a tape. At the end of the manufacturing,this tape is advantageously stored on a coil or a support which may bedirectly used on the deposition automata (robot). The winding may be ofthe wire-to-wire type (the tape is wound edge-to-edge, this method ispreferred) or of the crossed type.

The filaments forming the strand or the tape are preferably continuousfilaments. The filaments used generally have a substantially circularcross-section (round filaments) or, preferably substantiallyparallelepipedal or elliptical sections (flat filaments). The strandshave irregular widths, as described in the table below, giving the widthof the carbon strands according to the number of filaments and to theirtiter.

Number of filaments Titer (tex) Width variation of a strand  3K 200 1 to3 mm 12K 445 2 to 5 mm 800 3 to 7 mm 24K 1000 5 to 10 mm 1600 5 to 12 mm

Any type of carbon thread may be used. Preferably, High Resistance (HR)threads may be used, for which the tensile modulus is comprised between220 and 241 GPa and for which the stress at breakage in traction iscomprised between 2,450 and 4,830 MPa, Intermediate Modulus (IM) threadsfor which the tensile modulus is comprised between 242 and 300 GPa forwhich the stress at breakage in traction is comprised between 3,450 and6,400 MPa and High Modulus (HM) threads for which the tensile modulus iscomprised between 345 and 600 GPa and for which the stress at breakagein traction is comprised between 3,450 and 5,520 MPa (see ASM Handbook,ISBN 0-87170-703-9, ASM International 2001).

In a), it is stated that the tension is handled or adjusted between bothcoils, which means that the strand and the tape which resultscontinuously are maintained under tension between the supply coil andthe storage coil. The tension all along the line and of the method mayvary according to the steps and devices the strand, and then the tapeare passing through. This tension may notably be comprised and varybetween about 5 and about 50 N. The guiding of the strand in step b)allows its accurate alignment in the machine axis. The guiding step maynotably suppress the transverse winding of the strand and/or remove theside movements related to the unwinding of a crossed wound strand on thesupply coil. The guiding may notably use at least one set of at leasttwo bars oriented so as to be able to bring back the strand stemmingfrom the supply coil, onto a perfectly aligned line or trajectory on themachine axis (the positioning in the axis includes the positioning at adetermined height, which is that of the machine axis), at least untilcooling of the impregnated tape. For example, a set of two bars at 90°may be used. The first bar is parallel to the axis of the coil, orientedat 90° relatively to the direction of running of the strand, the lattersliding from left to right on the first bar because of the transversewinding of the supply coil. This first bar gives the possibility ofadjusting the alignment of the strand in the remainder of the method. Italso gives the possibility of forcing the strand to flatten, notably,but not only, in the case of a round initial strand. Then, the strandpasses in contact with the second bar located below the first, orientedat 90° relatively to the previous one and perpendicularly to the machineaxis, and which gives the possibility of keeping the strand flat andadjusting the height of the strand for the continuation of the method.

According to a first embodiment, the strand originally has a widthconstantly greater than the width of the final tape.

According to a second embodiment, the width of the strand is constantlyor occasionally (one/off) equal, close or lower than the width of thefinal tape. In this case the spreading of the strand in step c) isprovided. The strand returned into the machine axis is spread outtransversely. The transverse spreading of the strand is accomplished ata width greater than the rated width of the tape. This step guaranteesthat the strand, gradually as it is subject to this step, always has awidth greater than the rated width of the final tape. To do this, thestrand may notably pass into a spreading device, comprising one orseveral bar elements, such as spreading bars, which give the possibilityof spreading the strand so that its width is always greater than therated width of the final tape. It is notably possible to use bars havinga diameter comprised between about 10 mm and about 100 mm. Preferably,the bars have a not very abrasive surface, for example chromium,aluminium or ceramic. In order to obtain the desired width, it ispossible to heat the bars and/or have them vibrate, which enhances thespreading.

In d) the width of the strand is handled or adjusted, which means thatthe width of the strand is reduced to a predetermined value by passingit in a calibration device. In the case of the strand spread out in c),the width is reduced to a predetermined value, notably comprised betweenthe maximum spreading out width and the rated width of the final tape.In order to carry out this handling of width, it is notably possible tohave the strand pass into a groove which calibrates the strand to thedesired width. Notably, the width after spreading is of about 1.5 toabout 4.5, for example from about 2 to about 3 times the rated width ofthe final tape. For example, the calibration width is from about 10 mmto about 29 mm for a rating of the tape of about 6.35 mm.

Downstream from this step, at a moment of its path, wherein the strandis under a strong tension (there may be a tension ranging up to 5 kg perstrand), it is preferable in step e) to pull the strand in order tomaintain its width and to apply to the strand a movement for advancingtowards the storage coil. This step may notably be accomplished by meansof a device giving the possibility of pinching the strand and of forcingit to move in the direction opposite to the supply coil. It is notablypossible to use a foulard or a similar device.

The work produced on this strand up to now gives the possibility ofworking with initial strands of very different qualities, for examplehaving a variable width, of guaranteeing a regular powder level and ofsignificantly improving the dispersion of width of the final tape.

A step for measuring the width may be accomplished with a laser, as thiswill be described later on.

The running rate of the strand and of the tape may be notably comprisedbetween about 5 and about 50 m/min, notably between about 10 and about40 m/min, typically between about 15 and about 35 m/min. This speed isadapted to the different steps, in particular the powder coating step.

The grounding f) of the strand, in order to allow electrostatic powdercoating, is advantageously achieved as close as possible to the powdercoating, therefore just upstream from this step.

The powder coating step g) determines the distribution of the matrix inthe final tape as well as the fiber/matrix level in the final compositeproduct. Preferably, an electrostatic powdering method is used. Thestrand is grounded, notably by passing into contact with one or severalbars which are grounded, for example one or several spreading bars.

This powdering step comprises a first dry fluidization step.Fluidization consists of having a gas pass between polymeric particlesof a small size. When the friction of the gas generates a sufficientforce for compensating the weight of all the particles of the bed, it isstated that the particle bed is fluidized. The use of the dry fluidizedbed gives the possibility of depositing larger amounts of powder and ofworking with more powder as compared with pressure pots.

One or several guns or nozzles for electrostatic powder coating arepreferably used, using the corona discharge principle. This consists ofapplying a high potential difference between the tip of the gun and thepart to be covered, which is connected to the ground. The electric fieldat the tip accelerates the electrons of the surrounding medium byCoulomb's force and ionizes the molecules present in the air. By anavalanche effect, a self-sustained method is obtained which makes thesurrounding medium conductive. The powder particles crossing thisionized medium become charged by accumulation of electrons at theirsurface. They are then driven by the electric field towards the strandwhich is connected to the ground. For the strands of non-conductivefilaments, the surface is made to be conductive before powder coating bynebulization, metallization or the use of a conductive polymer.

Within the scope of this invention, the deposition of the powder isaccomplished via the use of one or two gun(s) on which a nozzle,preferably a flat nozzle, is mounted. This type of facility gives thepossibility of generating a powder cloud around the strand which isitself connected to ground. The powder which is located around the fiberis then attracted by the strand modifying its trajectory for generatinga thin layer of deposit all around the strand. Preferably, a gun ispositioned above the strand, the other one underneath.

The control of the guns is accomplished via a central unit which allowsindependent control of both guns. The parameters which may be adjustedare:

-   -   Injection pressure: it gives the possibility of bringing the        powder of the fluidized bed to the gun    -   Dilution pressure: additional pressure which gives the        possibility of diluting the powder in the pipe which leads to        the gun.    -   Tension and intensity: both of these parameters give the        possibility of controlling the tension and the intensity        dissipated at the cathode.

The adjustment of these parameters gives the possibility of adjustingthe powder level deposited on the fiber and the regularity of thedeposit. The adjustments are to be adapted for each strand/matrix pair.

Possibly, the carbon tape is divided into several filament bundlesduring the powder coating. The use of this option makes it preferablethat a first powder coating pass is achieved vertically or in thevicinity of the strand separated into bundles, and that a second powdercoating pass is achieved a little further on, at a location of the linewhere the tape is again joined up (the contiguous bundles then havingtendency of moving closer to each other in order to tend towards thetape structure such as it was before the separation into bundles, exceptthat some polymer was deposited for which one portion may separate, moreor less distinctly, the contiguous bundles), in order to guarantee thecladding of the strand. The number of bundles and how to obtain them aretackled later on. More details on this embodiment are given in Example4.

Once the powder is deposited on the thread, this is then referred to asa tape, which therefore consists of a fibrous reinforcement oriented inthe longitudinal direction impregnated with a polymeric matrix. Thelength of a tape coil may be equal or substantially equal to the coilfrom which the thread stems, without any length limit on the thread.

The mass polymeric matrix level applied on the spread out strand maynotably be comprised between about 20, 25 or 30% and about 75%, notablybetween about 20, 25 or 30% and about 50% and more particularly betweenabout 30% and about 40%. This particularly high level gives thepossibility of using the tape in the indirect method. This level mayattain significant values, greater than 30 or 40%, while being flexibleand well consolidated, as this will be seen later on.

At the stage of the impregnation of the strand, the polymer whichimpregnates the fiber is in the form of a powder for which the grainshave a diameter notably comprised between about 10 μm and about 300 μmand preferentially between about 30 μm and about 200 μm.

The method may be applied to any type of fluidizable powder having asoftening point allowing adhesion to the strand during the powdercoating. From among these powders mention may more particularly be madeof the following thermoplastic and thermosetting polymers: polyamides(notably PA6, PAI2, PAU, PA6.6, PA 6.10, PA 6.12), co-polyamides (CoPA),polyamides-block ether or ester (PEBAX, PEBA), polyphthalamides (PPA),polyesters (notably polyethylene terephthalate—PET—, polybutyleneterephthalate—PBT—), the co-polyesters (CoPE), the thermoplasticpolyurethanes (TPU), the polyacetals (POM, . . . ), polyolefins (notablyPP, HDPE, LDPE, LLDPE), polyethersulfones (PES), polysulfones (PSU, . .. ), polyphenylene sulfones (PPSU, . . . ), polyetheretherketones(PEEK), polyetherketoneketone (PEKK), poly(phenylene sulfide) (PPS),polyetherimides (PEI), thermoplastic polyimides, liquid crystal polymers(LCP), phenoxys, block copolymers such asstyrene-butadiene-methylmethacrylate copolymers (SBM),butyl-methylmethacrylate methylmethacrylate-acrylate copolymers (MAM)and mixtures thereof, epoxys, bismaleimide, phenolic polymers.

According to a characteristic of the invention, the thermoplasticmaterial is a thermoplastic material. Firstly, this may be a highperformance thermoplastic material i.e. having a melting point or atransformation temperature greater than or equal to 280° C. It maynotably be selected from PEEK, PPS, PEKK, PEI, or a mixture of at leasttwo of them.

The invention is compatible with the use of thermosetting polymers as apowder having a softening temperature less than their cross-linkingtemperature. This type of powder is obtained by formulation of anon-cross-linked thermosetting polymer and gives the possibility ofobtaining a tape with a non-cross-linked thermosetting polymer levelcomprised between 20, 25 or 30% and 75%. This tape may then be used inan automated fiber-placement method or filamentary winding method, wherethe cross-linking will be activated once the cross-linking temperatureis reached. This tape impregnated with thermosetting polymer gives thepossibility of making composite parts without any injection or infusionstep after placement of the tape and also allows storage for a limitedtime at room temperature.

In step h), the melting or softening of the powder may notably becarried out by passing in one or several, notably 2, ovens, preferablyshort or medium infrared ovens, just after the powdering step. Theregulation of the oven(s) is accomplished preferably in power for abetter stability of the method. There again, the adjustments are to beadapted for each strand/matrix pair but also depending on the runningrate and the targeted powder level. The temperature applied to thepolymer is in every case greater than its melting point (e.g. forsemi-crystalline polymers) or sufficient for having the powdery polymerpass to the viscous state allowing the impregnation. For PEEK, thetemperature may notably be comprised between 300 and 450° C., moreparticularly between 350 and 450° C.

The calibration of the tape in step i) to a target width is adetermining characteristic since, for example, the width variationscause non-qualities at the moment of the automated deposition of thetape by the deposition automator for forming. A too small widthgenerates «gaps» while a too large width generates «overlaps» andjamming at the deposition head.

In order to obtain a low width dispersion, it is necessary to have aperfect thread alignment before calendering, which is ensured all alongthe method and at the calibration stage. Thus it is possible to provide,upstream from the melting, an alignment of the tape in order to have itcoincide with the machine axis and in particular with the calibrationdevice located downstream. It is thus possible to use one or severalbars, notably oblique bars.

Preferably, in step i), the tape may be calendered. This calendering maygive the possibility of alignment on the machine axis or contribute tothis. Especially, the calendering gives the possibility of ensuring theimpregnation of the strand with the thermoplastic or thermosettingmaterial, which is still found in the molten state. Preferably, thecalender is cooled. The temperature of the material at this stage mayallow it to become sufficiently fluid so as to be shaped. Thecalendering may be accomplished by having the tape pass between at leasttwo cooled rollers for which it is possible to regulate the pressure andthe temperature. In this device, the calendering gives the possibilityof having the matrix penetrate more or less into the tape and alsopossibly spreading out the tape.

The impregnation level takes into account the distribution of the matrixin the transverse direction of the tape. A low impregnation levelamounts to having, according to an embodiment, a hollow tape with adistribution of the polymer only at the periphery of the strand (e.g. incarbon), thereby forming a polymer sheath (or continuous layer) whichprotects the filaments and guarantees very great flexibility to thetape. In other words, one has a reduced proportion of filaments taken inthe polymeric matrix. In this embodiment, the calendering pressure ispreferably less than 1 bar, typically it is comprised between about 0.1and about 0.9 bars, notably between about 0.1 and about 0.6 bars. Thistype of product is of particular interest for the draping of complexshapes with very small radii of curvature.

On the contrary, a high impregnation level will correspond, according toanother embodiment, to a tape wherein the polymer is distributed in asubstantially uniform way between the filaments (e.g. of carbon) in thedirection of the width and of the thickness. In this case, the polymerprotects the filaments of the tape by a sheath, but then it does notnecessarily form a continuous outer layer like in the previous case.However one has a high proportion of filaments taken in the polymericmatrix. In this embodiment, the calendering pressure is preferablygreater than or equal to 1 bar, typically it is comprised between about1 and about 4 bars. By increasing the impregnation level, the sliding ofthe filaments against each other is prevented, which reduces theflexibility of the latter.

According to the invention, the temperature parameter may becontinuously tracked by the measurement of temperature, for example bymeans of an infrared pyrometer, at the outlet of the oven and/or beforethe calendering.

The calendering ensures a first calibration, notably in the thickness ofthe tape.

Step i) may comprise a calibration in width of the tape by passing in atransverse calibration device or in width, or calibration both in widthand in thickness. Preferably, step i) comprises on the one hand, thecalendering and on the other hand the calibration in width, or in widthand in thickness.

Preferably, calibration is made both in the transverse direction and inthickness. It is notably possible to calibrate by means of at least twoantagonistic forms of calibration, notably antagonistic grooves. Thecalibration is advantageously adjusted to the desired rated width forthe tape. Different embodiments will be described later on.

The cooling is carried out gradually between the outlet of the oven andthe coil. It is not indispensable to provide a cooling device. It wasseen that the calendering at the end of the calibration i) is carriedout at a sufficient temperature, e.g. comprised between the glassytransition temperature and the melting point of the semi-crystallinepolymer. Before the coil, the temperature reached is such that thepolymer is no longer deformable, for example it is less than the glassytransition temperature Tg of the semi-crystalline polymer.

The width and/or the thickness of the tape may be measured in j)continuously, preferably with its standard deviation, during themanufacturing of the tape by using the following method. Downstream fromits calibration and upstream from its storage on a coil, one/offmeasurements of width and/or of thickness are carried out every x cm(for example every 50 cm or every 1 meter) by means of a Laser, the dataare processed by a computer processing unit or a computer collecting thevalues of widths and calculating the standard deviation. Advantageouslya laser is used formed with an emitter emitting a laser light line and areceiver including a line of receiving cells. The emitter is placed onone side of the tape, facing one of its planar faces if the width ismeasured. The receiver is placed on the other side of the tape, facingits other planar face always for the measurement of width. The shadow ofthe tape projected on the receiver gives the possibility of determiningthe width (or the thickness) with great accuracy.

The coil in step k) consists of winding the tape on supports preferablycompatible with automated deposition automator. It may be carried out intwo different ways: in tension or in velocity. For the winding intension, the pin bearing the storage coil adapts its speed of rotationdepending on the tension information of the tape, for example rewound bya dancer arm. This type of coil gives the possibility of having a veryclean coil and does not require any subordination of velocity with thedevice, such as the foulard, which pulls the tape at the beginning ofthe line. In the case of a fast winding, the speed of the pin is enteredas a set value, the winding device has to be servocontrolled and thedriving device such as the foulard in order to avoid any problem oftension due to the difference in speed between both apparatuses. Atensioned coil is preferred.

The coil and therefore the speed for producing the tape may be comprisedbetween about 5 and about 50 m/min, notably between about 10 and about40 m/min, typically between about 15 and about 35 m/min.

The method described in the invention gives the possibility of making atape just from a single strand and from several strands (2 or more).

In an embodiment, the surface mass of carbon is increased. For this, atleast two, preferably two, carbon tapes are superposed in order toobtain a given surface mass. For example, two carbon tapes of 12K 800tex calibrated to 6.35 mm are superposed in order to obtain a surfacemass of 2×126=252 g/m². The association of both threads may beaccomplished before powdering at the spreading or after powdering, oncethe polymer has melted. In both cases, it is necessary to reproduce theunwinding and guiding elements described earlier. Next, in the firstcase, the mixture of the filaments of both threads is accomplished allalong the bar devices used for spreading the threads. The continuationof the line is not modified, only the adjustment of the electrostaticpowdering and the power of the ovens have to be adjusted. In the casewhen the assembling is carried out after powdering, the guiding of bothpowdered threads has to be adapted before calibration, the remainder ofthe line remaining unchanged.

Another object of the invention is the tape which may be produced by themethod of the invention. According to the invention, a continuousreinforcement tape is produced formed with unidirectional filaments ofan inorganic material, substantially uniformly coated and/orsubstantially impregnated to the core with a thermoplastic orthermosetting polymer at a mass level comprised between about 20, 25 or30% and about 75%, notably between about 20, 25 or 30% and about 50% andmore particularly between about 30% and about 40%. The tape is of apredetermined and controlled constant width with preferably a standarddeviation comprised between 0.02 and 0.15 mm, preferably between 0.02and 0.05 (limits included), on a length of a single piece (without anysplice) greater than or equal to 100, 500, 1,000 or 5,000 m, or evenmore. This standard deviation exists in reality over the whole length oftape produced from a continuous supply strand length. From a coil with xmeters of strand, a tape with a length substantially equal to the widthand compliant standard deviation is produced. This standard deviation istypically measured as described above by a Laser measurement. The tapeis moreover continuous over the whole of its length, without cutting anyfilament and in a single piece, i.e. without any splice. Itsconstitutive filaments are substantially parallel to the longitudinaldirection of the tape (or perfectly aligned in the longitudinaldirection). This product is intended for indirect methods for producingcomposite parts, from one or several strands. The tape has a constantwidth, which may notably be comprised between about 2 mm and about 75 mmand more particularly between 5 mm and about 10 mm. The level ofthermoplastic or thermosetting material may attain significant values,greater than 30 or 40%, while being flexible and well consolidated, asthis will be seen later on. The standard deviation is calculated byusing the following formula:

$\sigma_{k} - \sqrt{\frac{1}{n}{\sum\limits_{i = 1}^{n}\left( {x_{i} - \overset{\_}{x}} \right)^{2}}}$

with n=number of measurements; x=average value of x; x_(i)=value of xfor n=i.

The width of the tape may be measured with its standard deviationcontinuously during the manufacturing of the tape by using the methoddescribed above, which gives the possibility of obtaining the standarddeviation over the total length of the tape or on a fraction. Outsidethe production line, in order to characterize a tape according to theinvention, it is possible to proceed in the same way, by unwinding thetape and by carrying out one/off measurements of width, for exampleevery 1 m by the laser measurement.

The object of the invention is also a continuous tape impregnated and/orconsolidated formed with unidirectional inorganic material filaments,preferably in carbon, uniformly coated and/or impregnated to the corewith a thermoplastic or thermosetting polymer, comprising a polymerlevel comprised between about 20, 25 or 30% and about 75%, notablybetween about 20, 25 or 30% and about 50% by weight and preferablybetween about 30% and about 40% by weight, based on the weight of thetape. This tape may notably appear in three forms which will bedescribed, i.e. hollow, impregnated and substantially consolidated tothe core, impregnated and substantially consolidated to the core withbundles of filaments. The tape has a constant width, notably with astandard deviation comprised between 0.02 and 0.15 mm, preferablybetween 0.02 and 0.05 mm (limits included). The width of this tape maynotably be comprised between about 2 mm and about 75 mm and moreparticularly between about 5 mm and about 10 mm. In an embodiment, thetape has an average width in the specification of 6.35 mm±0.15 mm with astandard deviation comprised between 0.02 and 0.05 mm, preferably over alength of one piece, that of the initial strand, notably greater than orequal to 100, 500, 1,000 or 5,000 m. Thus it is possible to have, forexample a tape with an average width of 6.35 mm with a standarddeviation comprised between 0.02 and 0.05 mm.

In a first embodiment, the tape is impregnated and consolidated at theperiphery, including on its two longitudinal edges, the thermoplastic orthermosetting material impregnating the filaments at the peripheryforming a substantially continuous sheath, including along the edges ofthe tape. Preferably, this tape has a particular surface condition,corresponding to the fact that it is covered in totality or in a majorportion with molten or softened polymer which substantially forms acontinuum of polymer from one end to the other of the tape in thedirection of the width, and in the direction of the length, asillustrated as an example in FIG. 6. The average thickness of polymer atthe surface (external layer) may advantageously be comprised betweenabout 10 and about 100 μm, preferably between about 25 and about 100 μm.The tape comprises a certain proportion of non-impregnated filamentswith polymer (taken in the polymer) at its inside. This proportion maynotably represent about 20, 25 or 30 to about 50% of the total of thefilaments of the tape (this may be determined by analyzing theimpregnated and non-impregnated surfaces by image processing of sectionswith adequate magnification; the observation with a microscope or anyother digital imaging device (still camera, video camera, etc.) givesthe possibility of distinguishing the areas of naked fibers of the areasof impregnated fibers and taken in the polymer, as well as the polymerareas substantially or totally without any filaments)). This tape issaid to be hollow, in so far that the core of the tape is formed withnon-impregnated filaments, the core being consequently non-impregnatedor non-consolidated.

In a second embodiment, the tape is impregnated and/or substantiallyconsolidated to the core, i.e. it comprises a high proportion offilaments impregnated with polymer in its inside. This proportion maynotably represent from about 80 to about 100% of the total of thefilaments of the tape. Preferably, this tape has a particular surfacecondition, corresponding to the fact that it is covered partly withmolten or softened polymer, forming discontinuous phases from one end tothe other of the tape in the direction of its width and in the directionof its length, as illustrated as an example in FIG. 7. This tape is saidto be impregnated to the core. According to an embodiment, theproportion of filaments taken in the polymer is comprised between 80%and 99, 98, 97, 96, 95 or 90%. Typical intervals are from 90 to 100%,notably from 95 to 100%. The average thickness of the polymer at thesurface (external layer) may advantageously be comprised between about10 and about 100 μm, preferably between about 25 and about 100 μm.

According to a particular embodiment of this impregnated tape andsubstantially impregnated to the core, the filaments are distributed asbundles. The filaments extend in the longitudinal direction of the tapeas at least two bundles of filaments separated and covered by thepolymer. The bundles are notably more or less individualized on thetransverse plane. It will easily be understood that the number ofbundles may be adapted according to the width of the tape. Typically 2to 50, notably 5 to 50, preferably 10 to 30 bundles may be provided. Thebundles are notably separated from each other by the polymer alone orcontaining optionally sparse filaments. The impregnated product may becharacterized by a distribution of the filaments as bundles with a widthcomprised between about 200 μm and about 6,000 μm and a height comprisedbetween about 50 μm and about 250 μm, the spacing of which is comprisedbetween about 25 μm and about 100 μm. The fiber bundles are totally orpartly impregnated with polymer in order to form a tape which has strongcohesion in the transverse direction to the fibers. Further, thisproduct retains a thin sheath (external layer) of polymer. The averagethickness of polymer at the surface may advantageously be comprisedbetween about 10 and about 100 μm, preferably between about 25 and about100 μm.

The measurement of the impregnation level may be conducted by imageanalysis (use of a microscope or still camera or digital camera,notably), of a cross-section of the tape, by dividing the surface of thetape impregnated with the polymer by the total surface area of theproduct (impregnated surface area+surface area of the porosities). Inorder to obtain an image of good quality, it is preferable to coat thecutout tape in its transverse direction in a standard polishing resinand to polish with a standard procedure allowing observation of thesample with a microscope with 6× magnification at least. As regards theimpregnation levels, typically: a hollow product: of about 30% to about70% and preferentially from about 40% to about 60%; impregnated product:from about 70% to about 100% and preferentially from about 90 to about98%; impregnated product with a bundle structure: from about 70% toabout 100% and preferentially from about 90 to about 100%.

The measurement of the thickness of the polymer sheath is carried outwith the same tools, notably by means of a microscope from across-section of the tape (the preparation of the sample is identicalwith the one intended for the measurement of the impregnation level).

The flexibility of the tape may be characterized by a rigidimeter TaberModel 150D (Taber Industries, North Tonawanda, N.Y., USA) according tothe NF ISO 2493-2 standard (Part 2: Taber Tester). All the measurementsare carried out with the caliber no. 1, a so called extreme sensitivitycaliber, the flexion angle used is 7.5° and the average of the referenceplatelet is 88.3 TSU (Taber Stiffness Unit) for a rated one of 88 TSU.

The Taber rigidity of the hollow tape with a mass of 250 TU (Taber Unit)is comprised between about 5 TSU and about 25 TSU and more specificallybetween about 10 TSU and about 20 TSU.

With this same device, the rigidity of the tape impregnated to the coreis comprised between about 45 TSU and about 65 TSU and more specificallybetween about 50 TSU and about 60 TSU. The same measurement may becarried out with a mass of 500 TU on the impregnated tape to the core,the Taber rigidity is then comprised between about 20 TSU and about 40TSU and more specifically between about 25 TSU and about 35 TSU.

This is to be compared with the Taber rigidity of a tape obtained bystandard impregnation (impregnation bath), which is typically comprisedbetween about 65 TSU and about 85 TSU and more specifically betweenabout 70 TSU and about 80 TSU.

A tape according to the invention with a proportion of filaments takenin the polymeric matrix of less than 100% has the remarkableparticularity of not breaking when the latter is folded on itself,unlike the tapes obtained by standard impregnation in a liquid phase.Without intending to be bound to theory, it is believed that aproportion of filaments, notably of carbon, which are not set in thematrix, may slide on each other during the deformation of the tape. Thetape according to the invention having a proportion of filaments takenin the polymeric matrix of less than 100%, preferably less than or equalto 99, 98, 97, 96, 95 or 90%, does not break during folding, which isnot the case of tapes obtained by standard impregnation which may breakwhen they are folded on themselves. The result of this is that the tapesaccording to the invention have an unparalleled folding capability, witha very reduced radius of curvature.

The object of the invention is also a facility giving the possibility ofapplying the method according to the invention and producing a tapeaccording to the invention. This facility notably comprises thefollowing elements.

a) At least one coil-holder pin with a brake.

b) A device for unwinding and/or aligning the thread in the machineaxis; alternatively, if one has a strand supply coil without anywinding, the device is a device for aligning the thread in the machineaxis; the device may for example include a set of two bars at 90°, afirst bar parallel to the axis of the coil, oriented at about 90°relatively to the running direction of the strand leaving the coil, anda second bar located below the first, oriented at about 90° relativelyto the previous one and perpendicularly to the machine axis, asdescribed above.

c) optionally a transverse device for spreading out the strand, notablya bar device operating on the principle of applying a tension on thestrand causing transverse spreading of the filaments, notably of thetype including at least 1, preferably several (typically from 2 to 7)bars perpendicular to the machine axis and including at least 1 which islocated above or below this machine axis (which gives the possibility ofimposing a tension to the strand, causing its opening); the bars maynotably have a diameter comprised between about 10 mm and about 100 mm;preferably they have a not very abrasive surface, for example inchromium, aluminium or ceramic; they may be heated and/or be vibrated;they may have a regular cylindrical, oval or elliptical shape or with anon-constant section, they may be rectilinear or bent, they may bebraked or not.

d) A device for calibration in width, giving the possibility of handlingor adjusting the length of the strand. This device may notably comprisea part provided with a groove for bringing back the filaments of thestrand to the width of the groove. The width of the groove may beadvantageously determined by the width of the tape to be produced, forexample, the calibration width (or of the groove) is from 1.5 to 4.5,notably from 2 to 3 times the rated width of the final tape.

e) Optionally a device for pinching or pulling the strand, preferablyincluding two rollers, at least one of which is driven into rotation,for example by a foulard or a similar device, giving the possibility ofpinching the strand in order to maintain its width and to apply to thestrand a movement for advancing towards the storage coil; the foulard orsimilar device may notably include at least two rollers positioned aboveeach other, at least one of them may be displaced towards the other inorder to apply a pressure to a material, in this case the strand, whichwould pass between them, and at least one of which is driven intorotation.

f) Optionally a device for measuring the width of the strand, notably alaser, as described above.

g) At least one metal part (preferably in a good electricity conductivemetal and with a non-abrasive surface) grounded. This metal part mayadvantageously be placed as close as possible to the powder coatingdevice which will be described. This may be one or several (typically 2)metal bars.

h) At least one electrostatic powdering device or electrostatic powdercoating device. Preferably the powdering device includes a fluidizer ora dry fluidization device with a chamber for storing powder maintainedin the fluidized condition. Preferably, it includes a powdering chamberin which are positioned one or several guns or nozzles for electrostaticpowdering using the principle of a corona discharge. The guns or nozzlesare connected to the chamber for storing powder fluidized by tubes.Preferably, the powder coating device comprises a central control unitfor the gun(s), giving the possibility of notably adjusting theinjection pressure, the dilution pressure, the tension and thedissipated intensity at the cathode. Details of the operation are givenabove.

i) Optionally a system for dividing the carbon tape into several bundlesof filaments under the powder coating device. This system for dividingthe initial tape may be accomplished by using a comb or any othergrooved element (for example a bar, the surface of which has streaks orgrooves extending on the circumference of the bar) giving thepossibility of separating the filaments in a regular way (examples ofnumber of bundles above, and therefore of grooves or the like). The goalis to deposit the powder at the core of the strand in order to increasethe impregnation level.

The use of this division device makes it preferable that the firstpowdering gun be placed vertically or in the vicinity of the tapeseparated into bundles, therefore vertically or in the vicinity of theseparation device or immediately downstream, and that the second isfound further on downstream in the powder coating device, at a locationwhere the bundles are brought closer to each other, this second gungiving the possibility of cladding the tape. The specific locationwithin the powder coating device may be easily determined.

j) At least one heating unit such as an oven. Preferably one short ormedium infrared oven(s) are used. The regulation of the oven(s) ispreferably accomplished in power. Their power is adapted to the appliedpolymer.

k) Optionally, a device for aligning the tape for having it coincidewith the machine axis and in particular with the calibrator which willbe described. It is thus possible to use one or several bars, notablyoblique bars.

l) Optionally, a calender, preferably the calender is cooled. Thepressure applied by the calender is preferably adjustable.

m) A calibration device in the transverse direction and in thickness, itmay notably comprise at least two calibration forms, notably grooves,antagonistic grooves, i.e. one of the forms will act upon contact with afirst face of the strand, the other one in contact with the other faceof the tape. The width of the forms is advantageously adjusted to thedesired rated width for the tape. In an embodiment, a first groove isflared at the beginning, but has a rated width equal to the desiredrated width for the final tape, for example 6.35 mm. This groove is incontact with the lower or upper face of the tape. A second groove is incontact with the other face of the tape, it also has a rated width equalto the desired rated width for the final tape, for example 6.35 mm. Thisgroove may for example be machined on a roulette wheel. Both grooveshave to be perfectly aligned and may for example be mounted on vernierswhich allow a very accurate adjustment of their position, relatively toeach other but also relatively to the running of the tape. Differentembodiments will be described in the examples.

n) Optionally, a device for measuring the width of the tape, notably alaser, as described above and in the examples. This measurement devicemay preferably be connected to a computer or program processor foradjusting the measurement rate (for example every x cm, e.g. every 50 cmor every 1 meter), recording the measured values all along theproduction of a tape coil and/or calculate the standard deviation.

o) At least one storage coil-holder pin, preferably this pin is shiftedrelatively to the machine axis in the direction of the height, forexample by one or several (typically 2) return bars. This pin may bepart of a conventional winding device, giving the possibility of windingin a crossed way or thread to thread, for example. The pin may notablybe servocontrolled in velocity or in tension.

According to a preferred feature, the elements b), c), d), e), g), h),i), j), k) and l), also preferably n), are aligned on the machine axisso that the strand, and then the tape does not undergo any sensitivelateral displacement movement. Still preferably, the elements e), g),h), i), j), and k), also preferably d) are perfectly aligned on themachine axis, so that the strand, and then the tape does not undergo anylateral displacement movement or a sensitive movement in height. The barspreading device c) as for it is preferably positioned so that the inletand the outlet of the strand is accomplished by being perfectly alignedon the machine axis, laterally and also preferably in height.

Driving devices are provided. They comprise devices for driving intorotation the pin of the device for winding the formed tape. They alsocomprise the foulard or similar in e). These driving devices mayadvantageously be servocontrolled, giving the possibility of handlingthe tension of the strand and then of the tape, all along the productionline.

The facility may comprise several production lines giving thepossibility of producing simultaneously several tapes from severalstrands.

The invention also relates to the parts or composite articlesmanufactured from a tape according to the invention or producedaccording to the method of the invention. These parts or articles areformed totally or partly with the tape, the piece or the article havingbeen consolidated under hot conditions, for example in an autoclave orin an oven, after placing the tape so as to form the blank. In anembodiment, the part or article is exclusively or mainly formed with thetape according to the invention or produced according to the method ofthe invention.

The invention also relates to the use of a tape according to theinvention for the manufacturing of an article or composite part, andsuch a manufacturing method, comprising the placement of the tape inorder to form a blank, and then the consolidation of the part or articleunder hot conditions, notably in an autoclave or in an oven. The tapemay be placed edge to edge and/or superposed, the superposition may beaccomplished according to adapted angle(s). The placement may beachieved by automated fiber placement (AFP: Automated Fiber Placement)or by filament winding, pultrusion, braiding, 3D printing. The placementmay be accomplished on a support or a mold.

The numerical mark 1 refers to a strand coil 2, for example the carbonfilament strand. This coil is mounted on a pin (not shown), providedwith an adjustable brake. A first bar 3 is parallel to the axis of thecoil 1 and oriented at 90° relatively to the running direction of thestrand 2, the latter sliding from left to right on the first bar becauseof the winding effect of the supply coil 2. Subsequently, a second bar 4is located underneath the first, oriented at 90° relatively to theprevious one and perpendicularly to the machine axis. A series of sevenspreading bars is illustrated. Four of them referenced as 5 arepositioned so that the strand is tangent to their upper portion, thethree other referenced as 6 being placed beneath the machine axis andbringing the strand to be tangent with their lower portion by applyingto it a stress such that the strand is spread out in width. Acalibration device 7 has a groove in which passes the strand, which iscalibrated therein to the desired width. A foulard 8 is positionedsequentially to it, this foulard being designed for pinching the strand2 and forcing it to move in the direction opposite to the supply coil. ALaser device for measuring the width of the strand is illustrated as 9.Two metal bars 10 and 11 connected to the ground are in contact for one,10 with the lower face of the strand, for the other one, 11 with theupper face. These bars apply a certain pressure on the strand.

In 12, an electrostatic powdering unit is illustrated comprising twopowdering guns 13, supplied with fluidized polymer powder stemming froma fluidization device not shown. One of the guns has its spraying nozzleoriented towards a face of the strand, the other one towards the otherface of the strand. The unit is controllable in order to ensure thecontinuous deposition of a determined amount of thermoplastic orthermosetting material on the strand 2 which runs inside the enclosure.

The numerical mark 14 designates both infra-red ovens, preferably eithershort or medium, located one behind the other, which are controlled intemperature and this control is made for power. The impregnated strandwith molten polymer then passes into a cooled calender 15. The calenderincludes two rollers and a device for adjusting the pressure exerted bythe rollers on the strand which passes between them. The strand thenpasses into a calibration device 16, examples of which will be describedwith reference to FIGS. 2-4. A Laser device for measuring the width ofthe tape is illustrated as 17, it is connected to a computer orprocessor allowing the recording of the width and the calculation of thestandard deviation. The device carries out one/off measurements, atregular intervals, according to the will of the user. At the stage ofthe passage in front of the Laser device, the strictly speaking tape 18is formed. The tape is then managed by a device for winding a tape,comprising two idlers 19 and 20 and a storage coil 21 mounted on a pin(not shown) driven into rotation.

According to a significant feature, the active surfaces (in contact withthe strand or the tape) of the elements 4, 5, 7, 8, 14, 15, and 16 areperfectly aligned on the machine axis, so that the strand, and then thetape when it is formed, does not undergo any lateral or sensitive heightmovement.

In FIG. 2, a first embodiment is illustrated of a calibration devicewhich may be used, notably as a device 16 in the facility of FIG. 1. Itcomprises a plate 22 dug with a groove 23 formed of a flared portion 24and of a rectilinear portion 25. The width of the groove is equal to thewidth of the tape to be produced. The numerical mark 26 designates aroulette having a planar axisymmetrical surface with a width slightlyless than that of the rectilinear portion 25 of the groove in which itwill be inserted in part. During operation, it is understood that thestrand passes at the bottom of the groove 23 and that the roulette willapply a pressure on it inside the portion 25 of the groove 23. A device(not shown), for example a vernier, gives the possibility of carryingout this operation. This gives the possibility of adjusting the pressureexerted on the strand.

In FIG. 3, the same plate 22 is again found. At the place of theroulette 26, downstream from the plate, a roulette 27 is positionedincluding a peripheral groove 28 with a flat bottom, the width of whichis equal to the width of the tape to be produced. When operating, it isunderstood that the strand 2 passes at the bottom of the groove 23, andthen in the groove 28 of the roulette 27, which will apply a pressure onit. A device, for example a vernier, not shown, gives the possibility ofpositioning the flat bottom of the groove in height relatively to themachine axis in order to adjust the pressure exerted on the strand.

In FIG. 4, a succession of three roulettes 29 are used each including aperipheral groove 30 with a flat bottom, the width of which is equal tothe width of the tape to be produced. The first and third roulettes areplaced above the machine axis, the second one below. When operating, itis understood that the strand 2 passes into contact with the bottoms ofthe groove 30, at the lower portion of the first roulette, and then atthe upper portion of the second roulette, finally at the lower portionof the third roulette. A device, for example a vernier, not shown, givesthe possibility of positioning the flat bottom of the grooves in heightrelatively to the machine axis in order to adjust the pressure exertedon the strand.

EXAMPLE 1: Obtaining a Carbon/PEEK Tape With a Mass Polymer Level of 34%and With a Width of 6.35 mm by Using the Facility of FIG. 1

One starts with a flat strand of carbon filaments HR HTS45 E23 from TohoTenax, a titer comprised between 810 tex and 780 tex, the strand widthvarying between 3 and 7 mm, wound and crossed.

A PEEK 150PB powder from Victrex, grain size d₁₀=30 μm, d₅₀=60 μm,d₉₀=100 μm.

The strand of carbon fiber is heated and then spreaded out to a widthcomprised between 8 mm and 12 mm by bar spreading, under a tension afterbar spreading comprised between 4.5 kg and 2.5 kg. The fibers then passinto a groove with a width of 10 mm, and then in the foulard which givesthe possibility of pulling the fiber. Before entering the powderingcabin, the fiber passes into the contact of two bars connected toground.

The powdering coating step is carried out by means of an SAMES facilitycomprising a fluidization pan, 2 guns and a controlled central unit. Inorder to obtain the targeted powder level, a single gun is used, itsadjustments are shown in the following table:

Parameter Adjustment Voltage (kV) 70 Intensity (μA) 70 Injectionpressure 12 Dilution pressure 5

The pressure of the fluidization pan is adjusted to 2 bars, which givesthe possibility of having a homogeneous and regular fluidizationconditions.

Next, the melting of the polymer is carried out by having the tape passbetween two infrared radians rollers with a tape (average IR) SOPARA,adjusted between 50% and 70% of their power. These are IR tape radiansof the brand SOPARA with a length of 75 cm and each with a power of 2.3kW.

The calibration is carried out by calendering in a first phase the tape,and then having it pass into a groove with a rated width of 6.35mm+/±0.05 mm.

The measurement of the width is carried out with a LASER Mike Model 911(measurement accuracy of 0.003 m), the data collected every 1 m duringthe production of a coil of 1,000 m are illustrated in FIG. 8.

The average width of the tape is 6.37 mm with a standard deviation of0.04 mm.

The winding is carried out in tension, at a value comprised between 15m/min and 20 m/min with a winding device SAHM.

FIG. 6 is a schematic view of the surface of the tapes observed with abinocular magnifying glass with a magnification of 0.6×3. The numericalmark 104 designates the polymer coating, relatively continuous, and onlyshows the carbon filaments on discrete areas designated by the numericalmarks 105.

EXAMPLE 2: Obtaining a Carbon/PEEK Tape With a Mass Polymer Level of 34%and a Width of 6.35 mm by Using the Facility of FIG. 1

One starts with a round strand of carbon filaments HM M46JB 12K 50B fromToray, a titer of 445 tex, a strand width varying between 2 and 5 mm,wound and crossed.

PEEK powder 150PB from Victrex, grain size d₁₀=30 μm, d₅₀=60 μm, d₉₀=100μm.

The strand of carbon fiber is heated in order to spread it out at awidth comprised between 5 mm and 8 mm by bar spreading, under a tensionafter bar spreading comprised between 4.5 kg and 2.5 kg. The fibers thenpass into a groove with a width of 8 mm, and then into the foulard whichgives the possibility of pulling the fiber. Before entering thepowdering cabin, the fiber passes into the contact of two bars connectedto ground.

The powdering coating step is carried out like in Example 1. Thepressure of the fluidization pan is adjusted to 2 bars, which gives thepossibility of having a homogeneous and regular fluidization conditions.Next, the melting of the polymer is carried out by having the tape passunder two infrared radians with a lamp SOPARA (length of 75 cm and eachwith a power of 3 kW), adjusted between 50% and 70% of their power.

The calibration is carried out by calendering in a first phase of thetape, and then by having it pass into a groove with a rated width of6.35 mm+/−0.05 mm.

The measurement of the width is carried out with the LASER Mike, like inExample 1, the collected data every 1 m during the production of a coilof 150 m are illustrated in FIG. 9.

The average width is 6.16 mm with a standard deviation of 0.13 mm.

The winding is carried out in tension, at a velocity comprised between 5m/min and 20 m/min with a winding device SAHM.

FIG. 7 is a schematic view of the surface of the tapes observed with abinocular magnifying glass with a magnification of 0.6×3. The numericalmark 106 designates the carbon filaments and this time, the polymerhaving remained at the surface does not form a quasi continuous coating,but discrete areas 107.

By comparison with FIGS. 6 and 7, FIG. 5 shows what one obtains with thestandard impregnation method by immersion in a bath. The numerical mark101 designates continuous areas of polymer at the surface, the mark 102designates discrete clusters of polymer and the mark 103 designatesnaked filaments.

EXAMPLE 3: Production of a Composite Article

An automated fiber placement automaton (AFP) is programmed fordepositing the tape according to Example 1 or according to Example 2 ona support, until the blank of the part to be manufactured is formed. Theautomaton places the tape edge to edge in order to thereby form a fold,and then superpose another fold on the preceding one, the superpositionbeing able to be accomplished according to adapted angle(s) according tothe production program for the blank. The formed blank is then placedaccording to a first sub-example in an oven and according to a secondsub-example in an autoclave. The consolidation is conducted to its endand the consolidated composite part is obtained.

Composite parts were formed successfully with the tape according toExample 1.

EXAMPLE 4: Production of a Tape With Bundles of Filaments

In the powdering device 12, a bar with circumferential grooves isinstalled, the grooves having a width which depends on the targetedwidth of the bundles; typically, this width may be comprised betweenabout 0.25 and about 2 mm. The tape is brought into contact with thisbar, in a permanent or intermittent way, in order to ensure theseparation of the strand into bundles. The first powdering gun projectsthe powder on the strand separated into bundles, notably immediatelydownstream from the bar. The second gun is positioned a littledownstream, notably a few centimeters further on, in a location wherethe bundles are brought closer to each other.

The impregnated product stemming from this application, schematicallyvisible in FIG. 10, is characterized by a distribution of the filamentsas bundles 108 with a width comprised between 200 μm and 6,000 μm and aheight comprised between 50 μm and 250 μm for which the spacing (polymerarea 109) is comprised between 25 μm and 100 μm. Further, this productretains a thin sheath 110 of polymer with a thickness comprised between25 μm and 100 μm. This product has good cohesion in the directiontransverse to the filaments. Its surface condition may be similar to theone observed with the hollow product.

What is claimed is:
 1. A continuous tape formed with unidirectionalfibers of an inorganic material and with a thermoplastic polymer matrix,said tape being impregnated to the core of said thermoplastic polymer,comprising a polymer level comprised between about 30% and about 75%,based on the weight of the tape, and having a constant width comprisedbetween about 2 mm and about 75 mm, with a standard deviation comprisedbetween 0.02 and 0.15 mm, over a length in a single piece greater thanor equal to 100 m.
 2. The tape according to claim 1, wherein the Taberrigidity of the tape with caliber no. 1, a mass of 250 TU and an angleof 7.5° is comprised between about 5 TSU and about 25 TSU, according tothe NF ISO 2493-2 standard (Part 2: Taber Tester).
 3. The tape accordingto claim 1, wherein the Taber rigidity of the tape with the caliber no.1, a mass of 250 TU and an angle of 7.5° is comprised between about 45TSU and about 65 TSU, compliant with the NF ISO 2493-2 standard (Part 2:Taber Tester).
 4. The tape according to claim 1, wherein from 80% to 99%of the filaments are taken in the polymer and sheathed by the latter. 5.The tape according to claim 1, wherein from 90% to 98% of the filamentsare taken in the polymer and sheathed by the latter.
 6. The tapeaccording to claim 1, wherein the inorganic material is carbon.
 7. Thetape according to claim 1, wherein the tape has an average width ofabout 6.35 mm with a standard deviation comprised between 0.02 and 0.05mm, over a length of a single piece greater than or equal to 100 m. 8.The tape according to claim 7, wherein the Taber rigidity of the tapewith caliber no. 1, a mass of 250 TU and an angle of 7.5° is comprisedbetween about 5 TSU and about 25 TSU, according to the NF ISO 2493-2standard (Part 2: Taber Tester).
 9. The tape according to claim 7,wherein the Taber rigidity of the tape with the caliber no. 1, a mass of250 TU and an angle of 7.5° is comprised between about 45 TSU and about65 TSU, compliant with the NF ISO 2493-2 standard (Part 2: TaberTester).
 10. The tape according to claim 1, comprising a thermoplasticpolymer which has a melting point or a transformation temperaturegreater than or equal to 280° C.
 11. The tape according to claim 10,wherein said thermoplastic polymer is selected from the group consistingof PEEK, PPS, PEKK, PEI and a mixture of at least two of them.
 12. Acontinuous tape formed with unidirectional fibers of an inorganicmaterial and with a thermoplastic polymer matrix, said tape beingimpregnated with said thermoplastic polymer, comprising a polymer levelcomprised between about 25% and about 75% based on the weight of thetape, comprising inside filaments which are not taken in the polymer inan amount of 20 to about 50% of the total of the filaments of the tapeand the polymer forms an outer continuous sheath of the tape.
 13. Thetape according to claim 12, wherein the Taber rigidity of the tape withcaliber no. 1, a mass of 250 TU and an angle of 7.5° is comprisedbetween about 5 TSU and about 25 TSU, according to the NF ISO 2493-2standard (Part 2: Taber Tester).
 14. The tape according to claim 12wherein the Taber rigidity of the tape with the caliber no. 1, a mass of250 TU and an angle of 7.5° is comprised between about 45 TSU and about65 TSU, compliant with the NF ISO 2493-2 standard (Part 2: TaberTester).
 15. The tape according to claim 12, wherein the tape comprisesa polymer level comprised between 30 and 70% based on the weight of thetape.
 16. The tape according to claim 12, wherein the tape comprises apolymer level comprised between 40 and 60% based on the weight of thetape.
 17. The tape according to claim 12, comprising a thermoplasticpolymer which has a melting point or a transformation temperaturegreater than or equal to 280° C.
 18. The tape according to claim 12,wherein said thermoplastic polymer is selected from the group consistingof PEEK, PPS, PEKK, PEI and a mixture of at least two of them.
 19. Afacility comprising: a) at least one coil-holder pin with a brake. b) anunwinding device and for aligning the thread in the machine axis. c) atransverse spreading device, d) a device for calibration in width, e) apinching and pulling device, f) optionally a device for measuring thewidth of the strand, g) at least one metal part grounded, h) at leastone electrostatic powder coating device, i) at least one oven, j)optionally, a device for aligning the tape to have it coincide with themachine axis, k) a calibration device in the transverse direction and inthickness, l) optionally, a device for measuring the width of the tape,and m) at least one storage coil-holder pin.
 20. The facility accordingto claim 19, wherein the powder coating device includes a dry fluidizerand one or several guns or nozzles for electrostatic powder coatingusing the principle of corona discharge.
 21. The facility according toclaim 19, wherein the calibration device comprises two calibrationforms, with one of the forms to contact a first face of the strand, theother one to contact with the other face of the tape.
 22. The facilityaccording to claim 19, wherein the calibration device comprises acalender.
 23. The facility according to claim 22, wherein the calenderis cooled.
 24. The facility according to claim 19, wherein thecalibration device comprises a calender and two calibration forms, withone of the forms to contact a first face of the strand, the other one tocontact with the other face of the tape.